The present invention relates to a system for transferring substrates into a clean room, having a box for receiving a cassette containing the substrates, with a box bottom which hermetically seals the box and which can be locked into and unlocked from the box by means of a locking mechanism. The locking mechanism has a pivot disk rotatably seated in the box bottom which, preferably by means of push rods, drives locking elements which engage locking slots in the box pivot disk has engagement bores which are engaged by locking pin of a turntable disposed in a lock gate and which, driven by an operating device of the system, perform a pivot movement triggering the locking and unlocking of the box bottom in the box, having a receiving frame for the positionally correct orientation of the box and a detent mechanism for fixing in place of the box in the receiving frame.
Such a system--identified by the technical term "Standard Mechanical Interface (SMIF)"--is known from U.S. Pat. No. 4,995,430. The serious disadvantage of this system is that the locking mechanism and the detent mechanism are embodied to be completely separated from each other. This has the disadvantageous result that it becomes necessary to provide complex electronic monitoring and control devices which are intended to assure that, on the one hand, locking of the box bottom in the box is only terminated once the box has been fixed in place in the receiving frame and, on the other hand, that the box bottom is locked in the box before the fixing in place of the box in the receiving frame is removed.
A further disadvantage of the known system resides in that here the operating device for locking and unlocking of the box bottom in the box by means of the turntable normally provided for this is disposed underneath the lock gate. This has the disadvantageous result that the known system cannot be integrated into clean room installations. Instead, the SMIF must be docked to the clean room installation. A separate lifting device is then required for lowering the lock gate. Furthermore, a separate transporting device is required, which transports the substrate cassette of the known system from the lowered lock gate to a lifting device of the clean room installation from where the further manipulation of the cassette with the substrates contained therein is performed. The separate lifting device required with the known SMIF systems and the transport device moving the substrate cassette from the lifting device of the SMIF to the lifting device of the clean room makes the construction of the known SMIF system more expensive and complicated in a disadvantageous way.
A further disadvantage rests in the complicated design of the locking mechanism. To achieve the tilting movement of the locking elements at the end of the locking process of the box bottom in the box, it is provided that the pins by means of which the push rods are linked with the pivot disk are guided in a cam way of the pivot disk so that by means of an elevation of the link point of the push rods a tilting movement of the locking elements is achieved. Such a structural solution is not only complicated and therefore expensive for producing the pivot disk along with the cam ways, it also disadvantageously increases the structural height of the box bottom. In addition, such a construction entails excessive wear of the pins and the cam way because of the increased material stresses thereon occurring in the course of the tilting of the locking elements.
A further disadvantage of the known system lies in its lack of consideration of the technical air requirements necessary in clean room installations to prevent the contamination of the highly sensitive substrates. No devices are provided in the known system which keep away airborne particulates which possibly have penetrated into the clean room. In this case this disadvantage of the known system has particularly serious effects because the lifting device itself, which is disposed in the clean room and which lowers the lock gate, brings such airborne particulates into the clean room: abrasion particles are generated around the lifting device which are subject to friction and which in the known system reach the portion of the clean room receiving the substrates in a disadvantageous manner.